Fungal infections of mucosal tissue are particularly troublesome because of the difficulty of effective administration of fungistatic or fungicidal agents, since systemic administration of such agents is not desirable and usually not effective. On the other hand, because of the normal fluid excretion from the mucosa there is a substantial tendency of these fluid excretions to wash out topically administered thereapeutic agents giving rise to the need for either high levels of administration which may lead to undesirable side effects or frequent administration which is not always possible and not alwasy adhered to by the patient. It is therefore desirable to seek fungistatic and fungicidal agents which when used in effective dosages overcome these problems.
There are three areas of concern to physicians and dentists, all involving a different problem of fungal infection. Under normal circumstances fungal infection of the oral cavity is not a problem since salivary clearance and oral hygiene, on a regular basis will not permit fungal infections to take hold. A major and important exception to this situation occurs among denture wearers. In 1956, Fisher (J. Prosthet. Dent., 6, 593 (1956) proposed that a connection might exist between poor denture hygiene and denture stomatitis. This relationship was demonstrated by Budtz-Jorgensen and Bertram (Acta. Ondontol. Scand., 28, 71 (1970). Further work by Budtz-Jorgensen (J.A.D.A., 96, 474 (1978)), showed that Candida albicans and related species play a major role in initiating, maintaining and aggravating the disease. He found, for example, that denture stomatitis is present in about 65% of the wearers of complete dentures in the Danish community. This work was confirmed by Tarbet in a United States study (J. Prothet. Dent., 48, 647 (1982)).
A recent survey of this problem was published by Budtz-Jorgensen as a review (Scand. J. Dent. Res., 82, 151-190) (1974)). In his review (at page 174), Budtz-Jorgensen discusses host defense mechanisms in Candida induced denture stomatitis and indicates that certain substances in saliva, for example, lysozyme, act to retard the growth of bacteria and fungi. However, he states (at page 175) that dentures prevent salivary anti-candidal substances from getting into contact with and combatting the flora propagating on the palatal mucosal surface. It has been suggested that C. albicans must be eliminated from the acrylic surface of the denture itself in order to halt the disease process (Davenport, Br. Dent. J., 129, 151 (1970)). These factors are critical to the design of antifungal agents for denture wearers since they must not only be active but also they must be effectively delivered and/or localized at the interface between the denture and the gum.
It has been previously reported that cationic histidine-rich polypeptides are present in human parotid saliva (Balekjian, Biochem. Biophys. Res. Com., 50, 676 (1973); Baum, et al., Arch. Biochem. Biophys., 177, 427 (1976); Peters and Azen, Biochem. Genet., 15, 925 (1977); and Peters, et al., Biochem. Genet., 15, 947 (1977). Azen (Biochem. Genet., 16, 79 (1978) however states that "he was unable to show biological or functional activity or toxicity of the purified salivary histidine-rich polypeptides. Studies include bacteriostatic, bacteriocidal or opsonizing effects against selected grampositive and gram-negative organisms in culture, the binding of mycoplasma pneumoniae to cell surfaces in culture, enzymatic activity, inhibitory effects against DNA and RNA viruses, toxicity or growth disturbances when injected into newborn rats and effects on ciliary function of the salt water shrimp."
While several different histidine-rich polypeptides, (hereinafter HRP) derived from the salivary glands have been reported and some have been partially sequenced (Peters and Azen, Biochem. Genet., 15, 925 (1977); Baum, et al., Arch. Biochem. Biophys., 177, 427 (1976); Baum, et al., J. Dent. Res., 56, 1115 (1977)), pure preparations have not heretofore been provided. Furthermore, to date, a biological role for the HRP has not been documented. As outlined in this application, the HRP as well as poly-L-histidine and synthetic L-histidine peptides, exhibit antimicrobial actions.
Although Yphantis, et al. (J. Bacteriol., 94, 1509 (1967)) have pointed out that Candida utilis is sensitive to the cationic polypeptide, poly-L-lysine, which is also antibacterial (Katchalski, et al., The Proteins II, p.405, 1964), Poly-L-lysine unfortunately is known to have unacceptable levels of toxicity in mammalian systems (see for example Rubini, et al., Proc. Soc. Exptl. Biol. Med., 82, 231 (1953)).
Other mucosal areas where Candida infections are prevalent are the vaginal and urethral mucosa. At the present time a limited number of antifungal agents are known which are used clinically with a reasonable measure of success, for example, nystatin and clotrimazole. However, since synthetic fungicides exhibit undesirable toxic side-effects, it would be preferable to use either the body's own naturally produced fungicides or agents structurally related to these natural body products. Naturally occurring agents may also serve to rduce the possibility of survival of resistant forms of the fungi. While fungal infection of the female is more common, current therapeutic methods also consider treatment of the male urethral mucosa, thus it would be desirable to provide compounds compatible therewith.